Allah The Almighty say : "Verily, Allah and His angels send blessings upon the Prophet: O you who believe! Send blessings upon him and salute him with all respect." (Qur'an 33:56)

Anas (May God be pleased with him) relates that the Messenger of Allah (May God exalt and bring peace upon him) said, "The ones closest to me on the Day of Judgement will be those who send blessings upon me abundantly." (Tirmidhi)

Learn more about the prayer on the prophet: www.ilmintensive.com/articles/022810_InvokingPeace.html

1st image:
Changed from the picture "Yellow flower": http://www.flickr.com/photos/doug88888/6911507528
of @Doug88888 : http://www.flickr.com/photos/doug88888/
Creative Commons Licensed photo: http://creativecommons.org/licenses/by-nc-sa/2.0/legalcode.uk

Thanks to the team of hisn-ul-muslim.com for the second image !!!